A common application for a radial seal is to seal the radial gap between a shaft and e.g. a bearing housing. The seal typically comprises an annular casing that is mounted in a bore of the bearing housing, and further comprises an elastomeric seal lip that is bonded to the metal casing. The seal lip bears against the shaft and makes sliding contact with a shaft counterface during rotation. Especially at high speeds, the shaft may rotate with a slight eccentricity, known as dynamic run-out, which in effect changes the radial gap between the counterface and the housing. To ensure that the seal lip remains in contact with the counterface, the seal is generally mounted with a very small clearance and the lip is spring-loaded. The radial load on the seal lip generates additional friction and the seal typically experiences uneven wear around the lip circumference.
One solution for removing the radial load on a seal is to execute the seal with radially overlapping parts and axially oriented seal contact surfaces. An example of a seal of this kind is disclosed in U.S. Pat. No. 4,348,031. The document describes a rotary fluid seal having a sealing ring arranged between axially opposed counterfaces of relatively rotatable members. The sealing ring has a pair of divergent seal lips which bear against the counterfaces, but are able to float freely between the relatively rotatable members. Upon relative rotation of the members, the sealing ring is frictionally driven into rotation by one or other of the members.
There is still room for improvement.